In the field of vehicle components it is often sought to reduce the weight of components, for example, in order to reduce fuel consumption. For example, sometimes lightening holes are made in crankshafts. These holes can be made by drilling different areas of the crankshaft.
FIG. 1 shows an example of a crankshaft 100, with a flange side 101 and a pulley side 102, with the main journals 103, crankpin journals 104, and counterweights 105. The crankpin journals may be distributed in different ways depending on the type of engine. For example, FIG. 2A shows a 180° layout, FIG. 2B a 120° layout, and FIG. 2C a layout at 90°.
FIG. 3 schematically illustrates a close-up of one of the lightening holes 107 of the crankshaft, which has been drilled in order to remove internal material from the crank pin 104 and, therefore, in order to reduce the weight of the crankshaft. However, the location and direction of the lightening holes 107 are important given that, for example, they can give rise to a higher risk of fractures, especially in critical points such as in zones close to the lubrication holes 106. As a result, the location and orientation of lightening holes 107 need to be calculated carefully. Consequently, as shown schematically in FIG. 4, a crankshaft may have multiple lightening holes 107, running in different directions. The machining of this type of multiple holes requires machines that allow the elements for machining to be positioned appropriately in respect to the machining tools, and that allow the machining tools to access the zones to be machined without encountering any obstacles. For example, it may be necessary to position the crankshaft in such a way that the direction of the hole to be drilled coincides with the direction of the corresponding machining spindle.
Many kinds of machines for machining crankshafts are known in the art. In these machines, the crankshaft is often held by its ends by devices that are arranged for rotating the crankshaft, cf., for example, U.S. Pat. No. 6,203,478-B1, EP-0397049-A2, and DE-19749939-A1. Although these devices or parts of them are sometimes arranged to allow for a certain axial displacement, basically, in parallel with the longitudinal axis of the crankshaft, as in the case of DE-19749939-A2, the crankshaft remains supported by its ends, and the elements interacting with the ends of the crankshaft can thus render access to certain portions of the crankshaft difficult, especially from certain angles.